Studies Directed Toward the Synthesis of the B-type Amphidinolide Natural Products Using Nickel-catalyzed Reductive Couplings of Enynes and Carbonyl Compounds PDF Download
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Author: Andrew Michael Lauer
Publisher:
ISBN:
Category :
Languages : en
Pages : 241
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Book Description
Progress coupling of substrates, toward the total synthesis of amphidinolide B1 is described. The reductive 1,3-eynes and ketones was explored. It was found to work well with simple but failed to yield intermediates toward amphidinolide B1 [images] ... The coupling of 1,3-enyne and aldehyde fragments toward the synthesis of amphidinolides G3 and H4 is also described. The entire carbon skeleton of these natural products has been prepared from this coupling and a subsequent installation of a methyl group using an indium based reagent ... [images].
Author: Andrew Michael Lauer
Publisher:
ISBN:
Category :
Languages : en
Pages : 241
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Book Description
Progress coupling of substrates, toward the total synthesis of amphidinolide B1 is described. The reductive 1,3-eynes and ketones was explored. It was found to work well with simple but failed to yield intermediates toward amphidinolide B1 [images] ... The coupling of 1,3-enyne and aldehyde fragments toward the synthesis of amphidinolides G3 and H4 is also described. The entire carbon skeleton of these natural products has been prepared from this coupling and a subsequent installation of a methyl group using an indium based reagent ... [images].
Author: Chudi O. Ndubaku
Publisher:
ISBN:
Category :
Languages : en
Pages : 482
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Book Description
The application of recently developed stereoselective nickel-catalyzed reductive coupling reactions of alkynes and aldehydes to the synthesis of complex natural product targets was explored. The "B-Type" amphidinolides were selected as ideal targets owing to their molecular complexity and the paucity of synthetically viable means for their total construction. The diastereoselective nickel-catalyzed reductive coupling of simple aryl-substituted alkynes and a-oxyaldehydes was developed and applied to the construction of the C15-C26 region of amphidinolide H3. ... Alternatively, the nickel-catalyzed reductive coupling reaction of 1,3-enynes and aldehydes was found to be a very effective way of installing the congested 1,3-diene moiety common to all members of this class of natural products. This methodology was further examined as a fragment coupling strategy for the syntheses of amphidinolides G3 and H4. This allowed for a highly convergent and functional group tolerant assembly of these ... molecules and, to date, stands as the most complicated setting for the application of the catalytic reductive coupling reaction.
Author:
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Category : Dissertations, Academic
Languages : en
Pages : 902
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Author: Elizabeth Anne Colby Davie
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ISBN:
Category :
Languages : en
Pages : 332
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(Cont.) A model for the stereoselectivity observed in the macrocyclizations is also proposed. ... amphidinolide T1 amphidinolide T4 * site of catalytic, stereoselective macrocyclization.
Author: Katrina Sue Woodin
Publisher:
ISBN:
Category :
Languages : en
Pages : 157
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Book Description
Catalytic Asymmetric Reductive Coupling of 1,3-Enynes and Aromatic Aldehydes Nickel-catalyzed reductive coupling reactions of 1,3-enynes and aromatic aldehydes efficiently afford conjugated dienols in excellent regioselectivity and modest enantioselectivity. These reactions were conducted in the presence of a catalytic ligand (R)-ferrocenyl(2-isopropylphenyl)phenylphosphine, whose overall synthesis was improved during the course of this investigation. 1-(Trimethylsilyl)-substituted enynes are shown to be efficient coupling partners in these reactions, and the dienol products formed readily undergo protiodesilylation under mild conditions. ... Catalytic, Asymmetric, Intramolecular Reductive Coupling of 1,1-Disubstituted Epoxides and Alkynes: Total Synthesis of Pumiliotoxin 209F and 251D Pumiliotoxins 209F and 251 D were prepared using a novel nickel-catalyzed intramolecular cyclizations between alkynes and 1,1-disubstituted epoxides. These cyclizations formed exclusively endo products without the use of a directing group on the alkyne. The synthesis of the reductive coupling precursors involved a diastereoselective sulfur ylide epoxidation of a proline-derived methyl ketone, where the choice of sulfonium salt conferred a major effect on the diastereoselectivity.
Author: Hugo M. Eng
Publisher:
ISBN:
Category :
Languages : en
Pages : 240
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Author: American Chemical Society. Committee on Professional Training
Publisher:
ISBN:
Category : Biochemistry
Languages : en
Pages : 1932
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Book Description
Faculties, publications and doctoral theses in departments or divisions of chemistry, chemical engineering, biochemistry and pharmaceutical and/or medicinal chemistry at universities in the United States and Canada.
Author: Brian J. Myers
Publisher:
ISBN:
Category :
Languages : en
Pages : 428
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Author: American Chemical Society
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ISBN:
Category : Chemistry
Languages : en
Pages : 1042
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Author: Nicholas Anthony Weires
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ISBN:
Category :
Languages : en
Pages : 560
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Book Description
This dissertation describes our efforts toward the total synthesis of welwitindolinone natural products, as well as the development of reactions involving the nickel-catalyzed activation of amide C-N bonds. The welwitindolinones have been long-standing targets in total synthesis for over two decades, and this dissertation describes two completed total syntheses of these alkaloids. In addition, several nickel-catalyzed transformations of amides are outlined, each of which demonstrate the powerful reactivity of nickel and highlight the utility of amides as synthetic building blocks. Chapters one and two present our enantiospecific total syntheses of the welwitindolinone alkaloids N-methylwelwitindolinone D isonitrile and N-methylwelwitindolinone B isothiocyanate. Our approach to these natural products features an aryne cyclization to construct the bicyclo[4.3.1]decane core of the molecules, as well as a C-H nitrene insertion reaction to introduce the bridgehead nitrogen substituent. In chapter one, a dual C-H functionalization event installs the challenging ether linkage and allows for completion of (-)-N-methylwelwitindolinone D isonitrile. In chapter two, a regio- and diastereoselective chlorinative oxabicyclic opening is detailed, which enables the first total synthesis of N-methylwelwitindolinone B isothiocyanate. Chapters three, four, and five describe the development of nickel-catalyzed carbon-carbon bond-forming reactions of amides. More specifically, chapters three and four outline the Suzuki-Miyaura couplings of aromatic and aliphatic amides, respectively, whereas chapter five details the alkylation of amide derivatives. These methodologies represent mild and complementary tools to the Weinreb ketone synthesis, proceeding through the nickel-catalyzed activation of the amide C-N bond. It is shown that amides, which were traditionally thought of as inert functionalities, can be utilized as synthons in C-C bond-forming reactions. Chapter six describes a method for the benchtop delivery of Ni(cod)2 involving the encapsulation of Ni(cod)2 in paraffin wax. Due to air- and moisture-sensitivity, Ni(cod)2 is normally handled under an inert atmosphere. Using our method of wax encapsulation, several nickel-catalyzed transformations are performed without the use of a glove box, including various amide C-N bond cleavage reactions. These studies are aimed at promoting the widespread use of nickel in transition metal catalysis. Chapter seven illustrates the kinetic modeling of the nickel-catalyzed esterification of amides. By developing a kinetic model, an optimization is undertaken that allows for the employment of catalyst loadings as low as 0.4 mol% nickel. This demonstration is intended to foster the advancement of kinetic modeling as a powerful tool in methodology development.
